A 61-year-old woman was seen with a 1-month history of a widespread eruption over the trunk and extremities. She also had an asymptomatic tumor in the neck that had developed 8 years earlier. Examination revealed generalized, erythematous scaling plaques over the trunk, arms, and extremities (Fig. 1). An ultrasound and radioisotope scan of the neck disclosed a soft tissue mass compatible with thyroid carcinoma.
Laboratory tests showed a white cell count of 9.8X109/L, and triiodothyronine, thyroxin, and calcium levels within the normal range. The thyroid-stimulating hormone (TSH) level was 6.3 μIU/mL (normal range 0.33–3.6 μIU/mL), and thyroglobulin was 320 μg/mL (normal range 14–31 μg/mL).
A skin biopsy specimen from the upper portion of the arm showed hyperkeratosis with focal parakeratosis and elongation of the rete ridges. The dermis showed mild papillary edema and perivascular lymphocytic infiltration compatible with psoriasis vulgaris. After the biopsy, ampicillin, 1000 mg daily, was administered for 21 days; however, the lesions were unchanged. The patient was then operated on with excision of the thyroid cancer and the regional lymph nodes. Histopathologic examination disclosed an adenocarcinoma of the thyroid; the lymph nodes were infiltrated by tumor cells. After the operation, cefazolin, 2000 mg daily, was given for 9 days. At 2 weeks postoperatively, the lesions began to subside without any dermatologic treatment and then resolved completely within 1 month of the operation (Fig. 2). Three weeks after the excision of the tumor, the patient started to receive levothyroxine sodium (T4), 0.1 mg daily, to compensate for low thyroid hormone production. Within the second postoperative month, TSH, triiodothyronine, and thyroglobulin returned to normal. After excision of the carcinoma, her psoriatic lesions, remained in remission for an additional 5 months without any dermatologic treatment.